JP2000222778A - Optical disk and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk in which an adhesive can be surely cured by increasing the transmitted amt. of UV rays and durability of the film thickness can be improved. SOLUTION: Reflection films 2, 2 are formed on two transparent substrates 1, 1 having signals. The substrates 1, 1 with the signals are laminated with an adhesive 4 with the reflection films 2, 2 facing each other. The reflection film 2 consists of an aluminum alloy and is formed to have the thickness >425 Åand <500 Å.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disk and a method for manufacturing the same. Specifically, the thickness of the reflective film is set to 42
By setting the thickness to be greater than 5 angstroms and less than 500 angstroms, it is possible to increase the amount of transmitted ultraviolet light and to ensure the curing of the adhesive.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk and a method for manufacturing the same, which are designed to improve the durability of the film thickness.

[0002]

2. Description of the Related Art As an optical recording medium for recording various kinds of information for audio and the like, there is an optical recording medium such as an optical disk whose recording or reproduction is performed by light irradiation. Fine irregularities such as phase pits and pregrooves for recording data information and tracking servo signals are formed on the layer. The information recording layer having the fine irregularities can be formed by an injection molding method or the like.

In an optical recording medium, first and second reflective layers are formed on a first substrate and a second substrate,
There has been proposed a configuration in which an adhesive film is interposed between them so that both substrates are matched with the first and second reflection films so as to be inside each other.

In this optical recording medium, data recording pits or pregrooves are formed on one main surface of the first substrate simultaneously with the molding of the first substrate by injection molding of a light-transmitting resin such as polycarbonate. Are formed, and a first reflection film is formed thereon.

On the other hand, by the same method as that of the first substrate, a second substrate having data recording pits on one main surface or second fine irregularities such as pregrooves is formed by injection molding. A reflective film is formed on the second fine irregularities to form a second reflective film.

Then, a second base is placed on the horizontal base of the rotary chuck.
The substrate is placed and held so that the center axis of the rotary chuck penetrates the center hole of the substrate, and the second reflective film is placed on the substrate, and a photocurable adhesive is applied on the second reflective film. I do. Next, the first substrate is placed through the center hole of the first substrate with the center axis of the rotary chuck penetrating therethrough, and the first reflection film and the second reflection film are aligned so as to be inside.

Next, by rotating the rotary chuck at a high speed, the photocurable adhesive interposed between the first and second substrates is uniformly stretched.

Then, light irradiation, for example, ultraviolet irradiation is performed from the first substrate side to cure the photocurable adhesive,
The first substrate and the second substrate are bonded together to form an optical disk having a structure in which the first substrate and the second substrate are bonded to each other.

[0009]

However, the following problems have been pointed out when pasting the above-mentioned conventional double-sided signal-attached bonded optical disk.

That is, if the reflection film is made thicker than necessary using an aluminum (Al) material, the amount of light transmitted through the adhesive that uses an ultraviolet curable resin is reduced,
The adhesive will not cure.

If the amount of ultraviolet light emitted is increased or the irradiation time is lengthened, the adhesive is cured, but the disk substrate is irradiated with a large amount of light, causing the disk to generate heat and causing warpage or damage to the substrate. It is not preferred because it becomes brittle.

Further, the adhesive cures even if the photosensitivity of the adhesive is increased. However, since the sensitivity is increased, the adhesive is hardened before bonding or when the surplus adhesive is reused. Therefore, it is not preferable because of lack of stability.

It has been experimentally confirmed that if the thickness of the reflective film is too small, the life of the reflective film is shortened.

There is also a method of increasing the light transmission amount by reducing the film thickness using gold (Au), silver (Ag), or the like, and obtaining a reflectance required for a disk. Since it is more expensive than (Al), it is not preferable in terms of manufacturing cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is possible to increase the amount of transmitted ultraviolet light to ensure the curing of an adhesive and to improve the durability of a film thickness. It is an object of the present invention to provide an optical disk and a method of manufacturing the same.

[0016]

The optical disk of the present invention comprises:
In an optical disk in which two signal-containing substrates each having a reflective film are bonded together, at least one of the reflective films is made of an aluminum alloy and has a thickness of more than 425 angstroms and less than 500 angstroms.

Further, the method for manufacturing an optical disk of the present invention comprises:
In a method for manufacturing an optical disc, comprising: a step of forming a reflective film on a signal-containing substrate; and a step of bonding the two signal-containing substrates to each other with the reflective films facing each other with an adhesive. , An aluminum alloy having a thickness of more than 425 angstroms and less than 500 angstroms.

According to the optical disk of the present invention and the method of manufacturing the same, at least one of the reflective films is made of an aluminum alloy and has a thickness in a range of more than 425 Å and less than 500 Å, so that the ultraviolet light in the reflective film can be reduced. The amount of transmission can be increased.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention relating to an optical disk and a method for manufacturing the same will be described below with reference to FIGS. FIG. 1 shows a cross section of an optical disk according to the present invention, that is, a bonded optical disk containing a double-sided signal.

In FIG. 1, two transparent signal-containing substrates 1, 1 are provided with reflection films 2, 2, respectively.
The signal-containing substrates 1 and 1 are respectively reflective films 2 and
2 are bonded to each other with the adhesive 4 so as to face each other. Here, the reflection film 2 is made of an aluminum alloy, and is formed so that the film thickness of the reflection film 2 is in a range of more than 425 angstroms and less than 500 angstroms.

FIG. 2 is an enlarged view of the example of FIG.
The signal is recorded by forming fine irregularities. Regardless of the shape of the unevenness, the thickness of the reflective film 2
It is formed so that it is always thicker than 425 angstroms and thinner than 500 angstroms.

Next, a method for manufacturing an optical disk will be described. First, first fine irregularities such as data recording pits or pregrooves are formed on one main surface of the first substrate simultaneously with the molding of the first substrate by injection molding of a light-transmitting resin such as polycarbonate. Then, the first signal-containing substrate 1 is formed.

Next, a second substrate having data recording pits on one principal surface or second fine irregularities such as pregrooves is formed by injection molding in the same manner as the first substrate. Then, the second signal-containing substrate 1 is formed.

Next, the above-described two signal-containing substrates 1, 1
The reflection films 2 and 2 are formed. That is, the first and second
The reflective films 2 and 2 are formed on the fine irregularities of the signal-containing substrates 1 and 1. Here, as a material of the reflection film 2,
Aluminum (Al) alloy (JIS4000-600
0) is used. This aluminum alloy (JIS4000)
-6000) are excellent in corrosion resistance. The material of the reflection film 2 is not limited to this aluminum alloy, but may be another material, that is, another metal or alloy having excellent corrosion resistance. Here, the thicknesses of the reflection films 2 and 2 were set to 450 Å.

The following two methods are available for forming a reflective film and adjusting the thickness of the reflective film. That is, one method is by sputtering.
In the case of performing the sputtering, as shown in FIG. 4, the film thickness can be adjusted by controlling the voltage applied to the aluminum (Al) target 7 during the sputtering and mainly the sputtering time. That is, the film thickness can be increased almost in proportion to the sputtering time.

Another method is based on the vapor deposition method. When the method is performed by the vapor deposition method, the film thickness can be adjusted by adjusting the amount of aluminum 12 as shown in FIG.

Next, the two signal-containing substrates 1 and 2 described above are used.
1 is bonded with an adhesive 4 with the reflection films 2 and 2 facing each other. That is, the second substrate is passed through the center axis of the rotary chuck through the horizontal base of the rotary chuck formed by the disk-shaped vacuum chuck of the spin coater, and the second reflection film is turned upward. , And held by a rotary chuck, and a liquid photocurable adhesive is placed on the second reflective film by, for example, dropping.

Here, a urethane / acrylate adhesive was used as the photocurable adhesive. It should be noted that the photocurable adhesive is not limited to a urethane-acrylate adhesive, and it is a matter of course that other photocurable adhesives can also be used.

Next, the center hole of the first substrate is made to pass through the center axis of the rotary chuck, and the first reflection film and the second reflection film are aligned so as to be inside.

Next, the rotating chuck is set to, for example, 100 rpm.
By rotating at a high speed of 0 to 4000 times, the photocurable adhesive interposed between the first and second substrates is stretched to a uniform thickness. Here, the thickness of the adhesive is 15 to
It is preferably in the range of 25 μm.

Thereafter, a photo-curing process is performed by irradiating the first and second substrates with, for example, ultraviolet rays while the photo-curable adhesive is interposed therebetween. This ultraviolet irradiation can be performed by an ultraviolet light source such as a metal halide or a high-pressure mercury lamp.

In the present invention, this photo-curing treatment is performed in the first step.
This is performed by light irradiation from the second substrate side together with light irradiation from the second substrate side. That is, light irradiation from both substrates is performed simultaneously.

In this example, that is, in the case where the reflection film has a thickness of 450 Å, two lamps each having an output of 1.5 KW were irradiated from both sides of the substrate for 7.0 seconds.
Alternatively, two lamps each having an output of 3.0 KW were irradiated from both sides of the substrate for 3.5 seconds.

As a result, compared with the conventional ultraviolet irradiation,
Improvements in the UV irradiation output and UV irradiation time could be observed. That is, regarding the improvement of the ultraviolet irradiation output, the conventional example, that is, when the thickness of the reflective film was 550 Å, the photocuring process could be performed by two lamps having an output of 3.0 KW. When the thickness of the film is 450 Å,
The photo-curing process was completed by two lamps having an output of 5 KW.
However, in both cases, the irradiation time is fixed at 7.0 seconds.

Regarding the improvement of the ultraviolet irradiation time,
Conventionally, when the thickness of the reflective film is 550 Å, the irradiation time is 7.0 seconds, whereas
In this example, that is, when the thickness of the reflective film was 450 Å, the irradiation time was improved to 3.5 seconds. However,
In both cases, two 3.0 KW output lamps are used.

In the above-described example, the photo-curing process is performed by irradiating light from the first substrate side and irradiating light simultaneously from the second substrate side. However, the method is not limited to this method. Absent. That is, for example, first, ultraviolet irradiation can be performed from the first substrate side, and then, at least two times of ultraviolet irradiation can be performed from the second substrate side.

Next, various evaluations were made on the optical disks manufactured by bonding as described above. This will be described below. That is, the contents of the evaluation items are the relationship between the aluminum film thickness and the ultraviolet transmittance, the relationship between the aluminum film thickness and the cured state of the adhesive, and the relationship between the aluminum film thickness and the durability of the coating film.

The cured state of the adhesive was evaluated by the following method. Here, the cured state of the adhesive was determined based on the magnitude of the peeling force of the optical disk. That is, the lower side of the end of the optical disk was fixed, a gauge was attached to the upper side, and the gauge was pulled upward. Then, the load when the optical disk was opened was determined. As a gauge, a digital hose gauge DPX-50TR (manufactured by Imata) was used.

Here, when the load is 350 g or more,
The cured state was evaluated as being good, and the result was indicated by a circle in the table. When the load was less than 350 g, the cured state was evaluated as poor, and the result was indicated by x in the table.

The durability of the reflection film was determined by the following method. Here, the determination is made based on a jitter (Jitter) change rate of the signal characteristics. That is, the optical disk was left under high temperature and high humidity for about 10 days, and the jitter values before and after that were measured. Here, for example, when the thickness of the reflective film is 450 Å or more, the jitter value is 6.5% before being left, whereas the jitter value is 7.0 after being left under high temperature and high humidity for about 10 days. 0%, and the rate of change of the jitter value is 108%.

On the other hand, when the thickness of the reflective film is 425 angstroms or less, the jitter value is 6.5% before being left, whereas the jitter value is 8 after being left under high temperature and high humidity for about 10 days. 0.0%, and the jitter value change rate is 123%.
Becomes Here, when the rate of change was 120% or less, it was evaluated that the durability was good, and the result was indicated by a circle in the table. When the rate of change was greater than 120%, the durability was evaluated as poor, and the result was indicated by x in the table.

The above evaluation items, ie, the relationship between the aluminum film thickness and the ultraviolet transmittance, the relationship between the aluminum film thickness and the cured state of the adhesive, and the relationship between the aluminum film thickness and the durability of the coating film are shown in the table. It is as shown in 1-3.

[0043]

[Table 1]

As can be seen from Table 1 showing the relationship between the aluminum film thickness and the ultraviolet transmittance, when the film thickness is 475 Å, the transmittance is as high as 0.8%, while the film thickness is 5%.
When the thickness reaches 00 Å, the transmittance decreases to 0.7%.

[0045]

[Table 2]

As can be seen from Table 2 showing the relationship between the thickness of the aluminum film and the cured state of the adhesive, the thickness of the reflective film was 5 times.
When the thickness is more than 00 Å, the amount of light to be cured becomes insufficient. In the initial stage where the thickness is exceeded, the adhesive immediately below the partially thick portion of the disk substrate is insufficiently cured, and when the thickness is further increased, the entire surface of the adhesive is cured. A deficiency occurs, which starts to oxidize the reflective film and impairs the reliability of the disk.
When the thickness of the reflective film was 475 angstroms or less, the cured state of the adhesive was good. From this result, it can be estimated that when the thickness of the reflective film is less than 500 angstroms, the cured state of the adhesive is good.

[0047]

[Table 3]

As can be seen from Table 3 showing the relationship between the aluminum film thickness and the durability of the film, the film thickness of the reflection film was 425.
Experiments have shown that when the thickness is less than Angstroms, the degree of oxidation of the reflective film rapidly increases, which impairs the reliability of the disk. On the other hand, when the thickness of the reflective film is 450 Å or more, the durability of the film is improved. Also, from this result, the thickness of the reflective film was 425.
When the thickness is larger than Å, it can be estimated that the durability of the film is good.

Therefore, these two defects can be avoided by limiting the thickness of the reflective film as described above. That is, it is preferable that the thickness of the reflective film be in a range of more than 425 angstroms and less than 500 angstroms. More preferably, the thickness of the reflective film is in the range of 450 Å to 480 Å.

In order to achieve such a limited reflection film thickness, in the case of performing the above-described sputtering, the voltage applied to the aluminum target at the time of sputtering is set to 500 to 55.
It is necessary to control the voltage in the range of 0 V and the sputtering time in the range of 1 to 1.5 seconds. In addition, when performing by the vapor deposition method,
The film thickness can be adjusted by adjusting the amount of aluminum.

As described above, according to the embodiment of the present invention, by setting the thickness of the reflective film to a range exceeding 425 Å and less than 500 Å,
By increasing the amount of transmitted ultraviolet light, the curing of the adhesive can be ensured. Further, the durability of the film thickness can be improved. That is, a proper life of the reflection film can be obtained. Also, since inexpensive reflective film materials can be used,
Cost can be reduced. Further, the irradiation time falls within the cycle time of another process, so that productivity is not impaired.

In the above example, the case where the thicknesses of the reflection films on both surfaces of the optical disk are more than 425 angstroms and less than 500 angstroms, respectively, is not limited to this. That is, as shown in FIG. 3, the film thickness of the reflection film on one side can be more than 425 angstroms and less than 500 angstroms. The other surface may have a thickness in excess of 550 Å, which is commonly used in the prior art.

Here, even when the thickness of one of the two reflective films is set to be more than 425 Å and less than 500 Å, the curing time of the adhesive is set to the cycle time required by the apparatus. Can fit.

The thickness of the two reflective films should be more than 425 Å and less than 500 Å, or 2
Whether the thickness of one of the two reflective films is more than 425 angstroms and less than 500 angstroms may be determined based on the configuration of the entire apparatus, cycle time, and the like.

Further, in the above-described example, the case where the present invention is applied to a disk-shaped optical disk, that is, a disk-shaped optical disk, has been described. However, the present invention is not limited to such an optical disk and a shape. The present invention can be applied to various optical recording media having fine irregularities such as a card, a sheet, etc. in an information recording layer. In addition, the present invention is not limited to the above-described embodiment, but can adopt various other configurations without departing from the gist of the present invention.

[0056]

The present invention has the following effects. Since the thickness of the reflective film is in a range of more than 425 angstroms and less than 500 angstroms,
By increasing the amount of transmitted ultraviolet light, the curing of the adhesive can be ensured, and the durability of the film thickness can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a bonded optical disk containing a double-sided signal.

FIG. 2 is an enlarged view of the example of FIG. 1;

FIG. 3 is a cross-sectional view of a bonded optical disc with a double-sided signal when the reflection film thickness is different.

FIG. 4 is a conceptual diagram of sputtering.

FIG. 5 is a conceptual diagram of vapor deposition.

[Explanation of symbols]

1 substrate with signal, 2, 3 reflective film, 4 adhesive, 5 sputter time timer, 6 applied voltage to target, 7 aluminum target, 8 vacuum chamber, 9 {Argon gas, 10} disk, 11} heater heating time timer, 12 aluminum, 13 vacuum chamber, 14 heater, 1
5 heater power supply

Claims (2)

[Claims] 1. An optical disk in which two signal-containing substrates each having a reflective film are bonded to each other, wherein at least one of the reflective films is made of an aluminum alloy and has a thickness of more than 425 angstroms and less than 500 angstroms. An optical disk characterized in that: A step of forming a reflection film on the signal-containing substrate; and a step of: bringing the two signal-containing substrates into contact with the reflection film,
Wherein at least one of the reflective films is made of an aluminum alloy and has a thickness in a range of more than 425 angstroms and less than 500 angstroms. Manufacturing method.